Interesting website...
SHELBY MEMORABILIA — VERNON ESTES CLASSICS
http://www.vernonestesclassics.com/memorabiliaandparts
All you need to do is buy a blank invoice ($45) on this site, get that old manual typewriter out of your garage and start typing using a real invoice as to correct content for a Cobra sale and VOILA! you have period correct invoice on the correct paper and typewriter.
Present this to someone or court and you to can be a CSX2049 owner.
Just playing around and found out how easy it is to get your hands on invoice material used by Shelby.
RIP CSX2049